In motor vehicle engines, fluids (fuel, cooling liquid, air conditioning liquid, hydraulic liquid for power assistance, windscreen washing liquid, . . . ) are transported by pipes to and from pumps and tanks via ducts made of synthetic material that are connected to functional members by means of a variety of connection devices.
The present trend for making such connections is to make use of so-called “quick” couplings which comprise rigid endpieces of complementary shapes, one secured to the duct and the other secured to the functional member, with one being engaged in the other and both behind held together by some kind of automatic latch.
There is necessarily a degree of functional clearance between these endpieces in order to enable them to be connected and disconnected easily, and in particular without using tools, and this clearance needs to be sealed in order to avoid leakage.
The sealing members used are quite effective with respect to the liquids that are transported, but these liquids contain multiple components, some of which are highly volatile and get round the seals that are put into place. The fluid circuit at this location is therefore more permeable than it is elsewhere, and it is in such coupling zones that high rates of emission to the atmosphere are observed, which emission can make the entire circuit unsuitable for complying with the prescribed standards or recommendations.